1. Field of the Invention
The present application is directed to an air brake system, and is more particularly directed to a double check valve commonly used in an air brake system. It will be appreciated, however, that the invention may be used in related environments and applications that encounter the same types of problems.
2. Discussion of the Art
Presently available check valves use a shuttle as the valve member that is interposed between a pair of inlet or supply passages. The shuttle selectively seals one of the inlets in response to air flow, and more precisely, the pressure differential imposed on the shuttle. The shuttle has a significant mass that includes an enlarged rubber core encased in a metal sleeve with elastomeric sealing ends extending from opposite ends of the sleeve for selective, sealing engagement about the inlet ports of the check valve assembly. In addition, a guide sleeve or tube is typically inserted in the valve body and includes side wall slots to allow air communication through the guide tube. The guide tube assists in selective axial movement of the valve member in response to the flow rate. Thus, the shuttle or double check valve member moves or shuttles between first and second positions depending on whether the pressure or flow rate is higher or lower than the other port. Due to the large mass of the currently used shuttle, the valve is typically mounted in a horizontal orientation for operation. If mounted vertically, a high flow rate is needed to move the shuttle upward and seal the port in the elevated position when air is supplied to the port located in the lower position. Thus, the vertically mounted check valve can encounter less than desirable operation of the valve, i.e., air can be bled from both inlets at low flow rates. Improvements are desired to assure that, in a system where two supplies feed a common delivery, the high pressure supply side will communicate with the delivery port and not communicate or flow into the low pressure supply side.
Moreover, the presently available assembly is relatively expensive because of the materials of construction and labor-intensive assembly features. Thus, in an effort to reduce the weight, as well as minimize the manufacturing cost, improvements are desired.